1. Field of the Invention
The present invention relates to a medium supplement for animal cell culture and an animal cell culture medium containing the same.
2. Background Art
In the field of life science, it has recently become important to produce useful substances in an industrial scale by mass culture of animal cells that produce a substance of interest, using cell culture technology or tissue culture technology. Animal cells of interest are cultured in this way with a culture medium which contains a basal medium which comprises amino acids, vitamins, inorganic salts, sugars and the like and an animal cell growth factor. As an animal cell growth factor, a serum component, such as bovine fetal serum and bovine calf serum, is generally used. Bovine fetal serum or bovine calf serum is in general needed to add to the basal medium at a level of about 5-20% by volume.
However, the serum component such as bovine fetal serum and bovine calf serum is limited in its supply and generally expensive. This will increase manufacturing cost of a product of interest. Also, serum tends to be different in its characteristics between lots, which is not desirable for culture that requires reproducibility. Further, it is sometimes difficult to purify a product from a culture supernatant of a culture medium containing the serum. Furthermore, safety of the product of interest may not be sufficiently guaranteed since there is a possibility that serum derived from animals may be infected with prions associated with mad cow disease, which is feared to cause Creutzfeldt-Jacob disease, and scrapie in sheep, as well as viruses.
Furthermore, when a medium containing serum is used in an experiment in the field of life science, the experimental system tends to become complicated, which may result in problematic confusion upon discussion of a causal relationship between cause and effect. This is because since serum comprises an extremely large variety of components including unknowns.
Therefore, attention has been drawn to cell culture media that contain known cell growth factors, hormones or the like instead of serum such as bovine fetal serum and bovine calf serum.
However, these cell growth factors or hormones are generally even more expensive than bovine fetal serum and bovine calf serum because their presence in nature is scarce, which limits their use.
Accordingly, there is a need for safe and relatively inexpensive cell growth factors or cell growth means, which can replace the abovementioned serum, known cell growth factors and the like.
In general, animal culture cells are classified into adhesive cells and suspension cells depending on their state in culture. Discussion has been made on stimulation of cell growth in animal cell mass culture by contriving appropriate means that suit to the state of cells in culture. For example, for adhesive cell culture, an attempt has been made to stimulate the cell growth by increasing adhesivity of the cells. Here, in order to increase the cell adhesivity, use of thin coating with collagen on the surface of a material of a cell culture bed has been discussed. However, the abovementioned risk of mad cow disease infection has to be contemplated since collagen is generally derived from cow, though it is relatively readily available.
Instead of the collagen-film coating treatment, use of a cell culture bed comprising silk film is suggested in Japanese Patent Laid-Open No. 11(1999)-243948 and Japanese Patent Laid-Open No. 11(1999)-253155. Such a culture bed can increase cell adhesivity and stimulate cell growth like the abovementioned collagen-coated bed; however, handling becomes complicated since a crystallization process is required to make silk protein insoluble upon film formation.
Thus, use of silk-derived components for a culture bed has been known, but use of components derived from cocoons, raw silk or the like for cell culture has not been discussed as far as the present inventors are aware.